The present invention relates to novel low molecular weight, structured polymer compositions. The invention also relates to methods for inhibiting scale formation, precipitation or deposition; increasing dispersion of insoluble precipitates in process waters; treating cooling and boiler water; and reducing the viscosity of mineral slurries using the aforementioned polymer compositions.
Industrial and residential waters contain naturally occurring contaminates (i.e., calcium, iron, barium, bicarbonate, carbonate, oxide, oxylate, sulfate, phosphate, zinc, etc.) that under conditions of use can chemically combine to form water insoluble precipitates. Additionally, water insoluble contaminates such as clay, silica and iron oxides can settle out of the water. These precipitates and inert materials can collect on surfaces of containers and piping in the form of deposits and scale, which reduce heat transfer, inhibit flow, increase likelihood of corrosion and enhance bacterial growth. In mining applications, compositions which aid in fluidizing insoluble particulates are desirable in order to more efficiently procure and transport the mined materials.
Current mechanisms for controlling scale and deposits involve preventing formation of insoluble precipitates (e.g., limiting crystal growth) or keeping inert insoluble materials dispersed in the system. Dispersants fluidize precipitates, silts, solids and combinations thereof. Chelants or sequestering agents can be used to bind cations to help prevent the formation of insoluble precipitates. Surface active agents can be used to aid in the dispersion of inert clays and silica. By nature, some of these agents may also be useful in fluidizing high solids slurries of ores and minerals.
Certain low molecular weight organic polymers (less than 100,000 MW) are capable of both inhibiting precipitation and keeping insoluble contaminates dispersed. These polymers are comprised of polycarboxylic and polysulfonic acids and their salts, copolymers of these acids, and co- and interpolymers of these acids with acrylamide, cationic monomers, vinyl esters and ethers.
In U.S. Pat. No. 3,463,730, Booth and Mead describe a process for controlling or preventing scale deposits in aqueous systems by addition of a low molecular weight (1,000-8,000) unhydrolyzed polyacrylamide. Booth and Cornelius, in U.S. Pat. No. 3,709,815 disclose polymers containing 2-acrylamido-2-substituted propane-1-sulfonic acid with an average molecular weight of at least 20,000 for use as boiler water dispersives and conditioners. In U.S. Pat. No. 3,898,037, Lange et al., describe polymers and co-polymers of acrylamido-sulfonic acid used in dispersing water-insoluble compounds of iron, calcium, magnesium, aluminum and commonly occurring particles of silt and clay. Amick et al., in U.S. Pat. No. 4,711,725, disclose a variety of copolymers, terpolymers and interpolymers also utilzed for these applications. In each patent, the polymers described are linear in structure and completely water-soluble.
Low molecular weight organic polymers that are linear and water soluble have also been disclosed to fluidize or disperse minerals in high concentration slurries. This allows more economical storage and transport forms of the minerals. Amick et al., in U.S. Pat. No. 4,711,725 demonstrates the abilities of co- and terpolymers of carboxylic and sulfonic acids to reduce the viscosity of clay and calcium carbonate slurries. Again, these polymer compositions have a linear structure and are water soluble.
Structured, high molecular weight polymers have been previously disclosed. Ryles et al., in U.S. Pat. No. 5,171,808, disclose cross-linked, anionic or amphoteric, organic, polymeric microparticles for use in flocculating dispersions of suspended solids. In European Patent Application 0 374 458, Neff et al. disclose water-soluble, branched polymeric flocculants based on polymerization of ethlyenically unsaturated monomers and branching agents in the presence of a chain-transfer agent. Both of these patents disclose compositions of high molecular weight polymers used as flocculating agents, and used to induce massing and precipitation of insoluble materials rather than dispersion of insoluble materials in a multiphase system.
While the aforementioned compositions utilized as scale inhibitors and dispersants may be applicable under specific conditions, they are only moderately effective or ineffective under certain circumstances. Therefore, a need exists for alternative compositions and methods for inhibiting scale formation, precipitation or deposition; increasing dispersion of insoluble precipitates in process waters; treating cooling and boiling water; and reducing the viscosity of mineral slurries.
This invention provides novel low molecular weight structured polymer compositions comprising ethylenically unsaturated monomers and structure-inducing agents. These structured polymers possess molecular structure that is branched, cross-linked or some combination thereof, as opposed to polymers that possess linear molecular structure. The structured polymers of this invention have improved capability for inhibiting the formation, precipitation or deposition of scale, improved capability of dispersing insoluble precipitates in aqueous systems, improved capability in treating cooling and boiler water, and improved capability to reduce the viscosity of mineral slurries compared to existing polymers.
It is a principal object of this invention to provide polymer compositions having a molecular weight of less than about 500,000 comprising at least one unsaturated organic monomer or salts thereof, and at least one structure-inducing agent.
Other objects of this invention are to provide: methods for inhibiting scale formation, precipitation or deposition in an aqueous medium comprising the step of adding to said aqueous medium an effective amount of a polymer composition comprising at least one unsaturated organic monomer and at least one structure-inducing agent; methods for increasing dispersion of insoluble precipitates in process waters comprising the step of adding to said process waters an effective amount of a polymer composition comprising at least one unsaturated organic monomer and at least one structure-inducing agent; methods of treating cooling and boiler water comprising the step of adding to said cooling and boiler water an effective amount of a polymer composition comprising at least one unsaturated organic monomer and at least one structure-inducing agent; and methods of reducing the viscosity of a mineral slurry comprising the step of adding to said slurry an effective amount of the polymer composition comprising at least one unsaturated organic monomer and at least one structure-inducing agent.
In order that the invention herein described may be more fully understood, the following detailed description is set forth. In the description, the following abbreviations are used:
The following terms are employed herein:
The term xe2x80x9cbranchingxe2x80x9d refers to the creation of branches or additional termini relative to the two original termini that exist in linear entities.
The term xe2x80x9cbranching agentxe2x80x9d refers to an agent which causes branching to occur.
The term xe2x80x9ccross-linkxe2x80x9d refers to an interconnection between polymer chains.
The term xe2x80x9ccross-linking agentxe2x80x9d refers to an agent which induces cross-linking, branching or a combination thereof to occur.
The term xe2x80x9cethylenically unsaturatedxe2x80x9d refers to the presence of at least one unsaturated ethylenic group.
The term xe2x80x9cinterpolymerxe2x80x9d refers to a polymer formed from three or more different monomers.
The term xe2x80x9cmonomerxe2x80x9d refers to single, discreet molecule which is capable of combining to form polymers.
The term xe2x80x9cstructured polymerxe2x80x9d refers to a polymer prepared with incorporation of a structure-inducing agent.
The term xe2x80x9cstructure-inducing agentxe2x80x9d refers to an agent which, when added to a polymer composition, induces branching, cross-linking or a combination thereof.
In view of the above definitions, other terms of chemical and polymer technology used throughout this application can be easily understood by those of skill in the art. Terms may be used alone or in any combination thereof.
This invention provides a polymer composition having a molecular weight of less than about 500,000 comprising at least one unsaturated organic monomer or salts thereof, and at least one structure-inducing agent.
In a preferred embodiment of this invention, each unsaturated organic monomer is independently selected from the group consisting of monoethylenically unsaturated carboxylic acids, monoethylenically unsaturated carboxylic acid anhydrides, monoethylenically unsaturated sulfonic acids, and sulfonated styrene. More preferably, each unsaturated organic monomer is independently selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, maleic anhydride, 2-acrylamido-2-ethylpropane sulfonic acid, 2-methacrylamido-2-methylpropane sulfonic acid, and allyloxy-2-hydroxypropyl sulfonic acid.
In another preferred embodiment of this invention, the structure-inducing agent is a crosslinking or branching agent. More preferably, the structure-inducing agent is independently selected from the group consisting of polyunsaturated acrylic amides, polyunsaturated acrylic esters, alkenyl-substituted heterocycles, tri- or tetra-allylic quaternary ammonium halides, and aldehydes. Even more preferably, the structure-inducing agent is independently selected from the group consisting of methylenebisacrylamide, triallylmethylammonium chloride, ethylene glycol diacrylate, glyoxal and formaldehyde.
In a further embodiment, this invention provides a polymer composition having a molecular weight of less than about 500,000 comprising a copolymer of unsaturated organic monomers and a structure-inducing agent.
In a preferred embodiment of this invention, the copolymer comprises unsaturated organic monomers independently selected from the group consisting of monoethylenically unsaturated carboxylic acids, monoethylenically unsaturated carboxylic acid anhydrides, monoethylenically unsaturated sulfonic acids and sulfonated styrene. More preferably, the copolymer comprises unsaturated organic monomers independently selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, maleic anhydride, 2-acrylamido-2-methylpropane sulfonic acid, 2-methacrylamido-2-methylpropane sulfonic acid and allyloxy-2-hydroxypropyl sulfonic acid.
In another embodiment, the copolymer comprises one unsaturated organic monomer independently selected from the group consisting of monoethylenically unsaturated carboxylic acids, monoethylenically unsaturated carboxylic acid anhydrides, monoethylenically unsaturated sulfonic acids and sulfonated styrene; and one unsaturated organic monomer selected from the group consisting of unsaturated acrylic amides, unsaturated acrylic esters, alkenyl-substituted heterocycles and unsaturated quaternary ammonium halides. More preferably, the copolymer comprises an unsaturated organic monomer selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, maleic anhydride, 2-acrylamido-2-methylpropane sulfonic acid, 2-methacrylamido-2-methylpropane sulfonic acid, allyloxy-2-hydroxypropyl sulfonic acid and sulfonated styrene; and an unsaturated organic monomer selected from the group consisting of acrylamide, substituted acrylamides, N-vinylpyrrolidone, methacrylate, ethylacrylate, and diallylic quaternary ammonium halides.
In another embodiment, this invention provides a polymer composition having a molecular weight of less than about 500,000 comprising an interpolymer of unsaturated organic monomers and a structure-inducing agent.
In a preferred embodiment, the interpolymer comprises at least one unsaturated organic monomer independently selected from the group consisting of monoethylenically unsaturated carboxylic acids, monoethylenically unsaturated carboxylic acid anhydrides, monoethylenically unsaturated sulfonic acids and sulfonated styrene; and additional unsaturated organic monomers independently selected from the group consisting of monoethylenically unsaturated carboxylic acids, monoethylenically unsaturated carboxylic acid anhydrides, monoethylenically unsaturated sulfonic acids, sulfonated styrene, unsaturated acrylic amides, unsaturated acrylic esters, alkenyl-substituted heterocycles and unsaturated quaternary ammonium halides.
More preferably, at least one unsaturated organic monomer is independently selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, maleic anhydride, 2-acrylamido-2-methylpropane sulfonic acid, 2-methacrylamido-2-methylpropane sulfonic acid, allyloxy-2-hydroxypropyl sulfonic acid and sulfonated styrene; and additional unsaturated organic monomers are independently selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, maleic anhydride, 2-acrylamido-2-methylpropane sulfonic acid, 2-methacrylamido-2-methylpropane sulfonic acid, allyloxy-2-hydroxypropyl sulfonic acid, acrylamide, substituted acrylamides, N-vinylpyrrolidone, methacrylate, ethylacrylate, and diallylic quaternary ammonium halides.
In an alternate embodiment, this invention provides a polymer composition having a molecular weight of less than about 500,000 comprising at least one unsaturated organic monomer or salts thereof, and at least one structure-inducing agent, wherein unsaturated organic monomers independently selected from the group consisting of monoethylenically unsaturated carboxylic acids, monoethylenically unsaturated carboxylic acid anhydrides, monoethylenically unsaturated sulfonic acids and sulfonated styrene comprise between about 50% and about 100% of the total composition and more preferably between about 70% and about 100% of the total composition.
In a further embodiment, this invention provides a polymer composition having a molecular weight of less than about 500,000 comprising at least one unsaturated organic monomer or salts thereof, and at least one structure-inducing agent, wherein the molecular weight of the polymer is less than 100,000 amu, and more preferably less than 50,000 amu.
In another embodiment, this invention provides a polymer composition having a molecular weight of less than about 500,000 comprising at least one unsaturated organic monomer or salts thereof, and at least one structure-inducing agent, wherein the concentration of structure-inducing agent is between about 50 and about 20,000 ppm.
In an alternate embodiment, this invention provides methods for inhibiting scale formation, precipitation or deposition in an aqueous medium; for increasing dispersion of insoluble precipitates in process waters; and for treating cooling and boiler water; comprising the step of adding to said aqueous medium, process waters and cooling and boiler water an effective amount of a polymer composition having a molecular weight of less than about 500,000 comprising at least one unsaturated organic monomer and at least one structure-inducing agent.
In another embodiment, this invention provides a method of reducing the viscosity of a mineral slurry comprising the step of adding to said slurry an effective amount of the polymer composition having a molecular weight of less than about 500,000 comprising at least one unsaturated organic monomer and at least one structure-inducing agent. In a preferred embodiment, the mineral slurry comprises one or more minerals selected from the group consisting of calcium carbonate, titanium dioxide, coal, calcined kaolin clay and hydrated kaolin clay. In an alternate preferred embodiment the mineral slurry comprises at least one metal, preferably a transition metal.
In alternate preferred embodiments, this invention includes the methods described above wherein the polymer composition comprises the preferred, more preferred and even more preferred polymer compositions described above.
The structured polymers described herein can be prepared by conventional polymerization techniques well-known to those skilled in the art. Such techniques include, but are not limited to, solution polymerization, reverse-phase emulsion polymerization and suspension polymerization. Polymerization may be initiated via a free radical initiator. The preferred initiator method is free radical, however, photochemical or radiation methods may also be utilized. The introduction of the structure-inducing agent may be performed either prior to, concurrent with or after combining the other agents necessary for formation of the structured polymers of this invention.
Where carboxylic acids, or their salts thereof, are used for the preparation of compositions of this invention, it is also envisioned that esters, amides or nitrites may be hydrolyzed to give the desired carboxylic acid. This hydrolysis may occur before or after a polymerization event.
In order to obtain the low molecular weight polymers of this invention, it is necessary to use a chain transfer agent in their preparation. Examples of chain transfer agents which may be used are well-known to those skilled in the art. They include, but are not limited to, agents such as alcohols, phosphites, phosphinic acids, sulfites, mercaptans, and thioacids. The amount of chain transfer agent necessary will be is influenced by factors such as efficiency of the compound, the monomer mixture used, the amount of structure-inducing agent present and the desired molecular weight of the final product. A combination of two or more chain transfer agents may be used in one formulation.